The objectives of this research are to identify and measure the forms in which human growth hormone, a family of peptides, circulate and to study the mode of action each form in man. The pituitary forms which have been identified in hGH preparations (and approximate percentages) are: Disulfide dimer (20-10); Major component or intact hGH of Li, (50-60); 20K (2-10); Slow GH (5-10); Slow-slow hGH (2-5); Fast hGH (5-10); Enzymically cleaved forms (5-10); deamidated; forms (5-10); and "diabetogenic factor". Radioimmunoassays of high specifity will be developed to establish the putative hormonal nature of each. Radioreceptor assays using membranes from different tissues will be used for establishing specific targets. Plasma will be fractionated to learn chromatographic characteristics of those forms found to circulate. The acute metabolic effects of each will be studied, as Investigational New Drug Status is achieved. These studies will seek to clarify the role of the pituitary in growth problems, diabetes and breast cancer.